The present invention relates to laser ablation to pattern a metallic layer, as well as an electrode for an electrochemical biosensor.
Electrochemical biosensors are well known. They have been used to determine the concentration of various analytes from biological samples, particularly from blood. Electrochemical biosensors are described in U.S. Pat. Nos. 5,413,690; 5,762,770 and 5,798,031; as well as in International Publication No. WO99/13101, each of which are hereby incorporated by reference.
An electrochemical biosensor typically includes a sensor strip. The sensor strip includes a space that holds the sample to be analyzed, may include reagents to be released into the sample, and includes an electrode set. The electrode set normally includes an insulating substrate, electrodes that contact the sample, which have contact pads for electrically connecting the electrodes to the electronics of electrochemical biosensor.
It is desirable for electrochemical biosensors to be able to analyze electrolytes using as small a sample as possible, and therefore it is necessary to miniaturize the sensor strip, as well as its parts, including the electrodes, as much as possible. Usually screen printing techniques have been used to form miniaturized electrodes.
Electrodes formed by screen printing techniques can only be formed from composition that are both electrically conductive and which are screen printable. Furthermore, screen printing techniques only allow for the reliable formation of structures and patterns having a feature size of approximately 75 xcexcm or greater. In addition, screen printing is a wet chemical process. It would be desirable to have a new method of forming electrodes which allows for the use of different composition, and which can form features smaller than 75 xcexcm.
Laser ablation is a technique using a laser to cut or mold a material. This technique usually uses a high power excimer laser, such as a krypton-fluoride excimer laser with an illumination wavelength of 248 nm, to blast away surface material. This technique has been used to ablate metals, polymers and even biological material, such as the cornea of the human eye. Such systems are well known to those of ordinary skill in the art, and are described in U.S. Pat. Nos. 5,576,073 and 5,593,739, each of which is hereby incorporated by reference.
In one aspect, the invention is a method of making a patterned laminate comprising ablating through a portion of a metallic layer with a laser. The metallic layer comprises at least one member of gold, platinum, palladium and iridium. Furthermore, the metallic layer is on, and in contact with, an insulating substrate, for example, a polymer.
In another aspect, the invention is a method of making a electrode set, comprising ablating through a portion of a first metallic layer with a laser, to form an electrode pattern. The first metallic layer is on an insulating substrate.
In still another aspect, the invention is a method of making an electrode set ribbon, comprising ablating through a portion of a first metallic layer with a laser, to form a plurality of electrode patterns. The first metallic layer is on an insulating substrate, for example, a polymer. The electrode set ribbon comprises a plurality of electrode sets.
In yet another aspect, the present invention is an electrode set, comprising a first metallic layer, on an insulating substrate, comprising a plurality of electrodes. The first metallic layer has a feature size of less than 75 xcexcm.
In yet another aspect, the present invention is a patterned laminate, comprising a patterned metallic layer on, and in contact with, an insulating substrate. The metallic layer comprises at least one of gold, platinum, palladium and iridium. Furthermore, the insulating substrate comprises a polymer, and the patterned metallic layer has a feature size of less than 75 xcexcm.
An advantage of the present invention is that it allows for the possibility of small feature sizes.
As used herein, the phrase xe2x80x9cpatterned laminatexe2x80x9d means a multilayered structure that includes an overlayer through which an underlying layer is exposed, i.e. the overlayer has gaps and does not completely cover the underlying layer. The gaps or areas of exposure form the xe2x80x9cpatternxe2x80x9d of the patterned laminate. Furthermore, the term xe2x80x9cpatternxe2x80x9d means one or more intentionally formed gaps having a feature size, for example, a single linear gap having a constant width, where the smallest width is the feature size. Not included in the term xe2x80x9cpatternxe2x80x9d are natural, unintentional defects.
As used herein, the phrase xe2x80x9cfeature sizexe2x80x9d is the smallest dimension of a gap found in a pattern.
As used herein, the phrase xe2x80x9celectrode patternxe2x80x9d is a pattern which when formed in a metallic layer includes at least two, for example 2 to 60, or 3 to 20, electrodes which are not electrically connected to each other, but each of which includes its own contact pad.
As used herein, the phrase xe2x80x9cmetallic layerxe2x80x9d refers to a layer made of a material that is a metallic conductor of electricity, such as a pure metal or alloys.
As used herein, the phrase xe2x80x9celectrode setxe2x80x9d is a set of at least two electrodes, for example 2 to 60, or 3 to 20, electrodes. These electrodes may be, for example, a working electrode and a reference electrode.
As used herein, the phrase xe2x80x9cablatingxe2x80x9d means the removing of material.
Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.